1. Field of the Invention
The present invention relates in general to subsea wellhead assemblies, and in particular to a wellhead housing, wherein an actuator mechanism causes the load on a casing hanger in the wellhead housing to be transferred to the housing even in the event the casing hanger may be set in a high position in the wellhead housing.
2. Description of the Prior Art
In a typical subsea well, wellhead housing is positioned on the floor of a body of water at the upper end of the well. The wellhead housing is a tubular member having a bore aligned with the well bore. A string of large diameter casing attaches to the lower end of the wellhead housing and extends into the well bore. After further drilling into the earth through the wellhead housing, a smaller diameter string of casing is installed. A casing hanger at the upper end of the smaller diameter string of casing is landed in the bore on a load shoulder in the wellhead housing.
Debris and cuttings from the well are a continuing concern in subsea wellhead equipment design and operation. The debris and cuttings can become lodged or located between the casing hanger and other load bearing structure in the wellhead, such as another casing hanger in a stack in the wellhead housing or the wellhead housing itself. Thus, there were concerns with proper seating of casing hangers for load transfer or sharing purposes. The problem became worse when several hangers were stacked on top of each other, as was typical in subsea wellheads.
For the uppermost, stacked hangers, the use of shim sets with adjustable shims was contemplated. Adjustments were to be made after appropriate measurements were made in the wellhead housing at the wellhead to determine the required amount of adjustment. However, a separate trip of equipment from the surface to the wellhead was required which was time consuming and thus expensive. There was also concern expressed about the ability to make accurate measurements to determine the required adjustment.